Water-assisted proton conductivity of two highly stable imidazole multi-carboxylate-based MOFs

Abstract

Two new chain-like metal–organic frameworks (MOFs), {[Mn(o-CPhH₂IDC)(4.4′-bipy)_0.5(H₂O)₂]·3H₂O}_n (1) (o-CPhH₄IDC = 2-phenyl(2-carboxyl)-1-H-imidazole-4,5-dicarboxylic acid; 4,4′-bipy = 4,4′-bipyridine) and {[Zn₅(o-CPhH₂IDC)₂(o-CPhHIDC)₂(2.2′-bipy)₅]·5H₂O}_n (2) (2,2′-bipy = 2,2′-bipyridine) have been designed and solvothermally or hydrothermally synthesized and structurally characterized. By SEM determinations and PXRD analyses, the high water stability and acid and alkali resistance of both MOFs have been determined. The affluent H-bond networks inside the frameworks formed by imidazole multi-carboxylate ligands and H₂O molecules would favor the transfer of protons. Furthermore, the temperature- and humidity-dependent proton conduction properties of the two MOFs were demonstrated. Also, the proton conducting mechanisms will be highlighted herein.